Fires and risks of fires in hazardous locations often require applications of large volumes of water or other extinguishing agents such as foam, compressed air foam, clean agents (gas), or dry chemicals, or combinations thereof. For safety, firefighters prefer to dispense these fluids from a sufficiently safe distance. This requires the fluids to be dispensed at high velocities, and the velocity through the nozzle in turn causes substantial nozzle reaction forces. These forces are often higher than can be resisted by human muscle power.
To absorb these reaction forces and transmit them to the ground or a substantially stationary object, fluid projecting devices called monitors are sometimes used. These monitors are arranged to direct the fluids in any of a range of desired trajectories, generally having at least one degree of freedom. Monitors generally include flow path designs and mechanisms that enable firefighters to adjust the trajectory easily and with little force.
The structural elements that enable a monitor to deliver fluid through a range of trajectories may be broadly divided into three classifications:                Swivel joints that form rotary unions;        Flexible flow paths that are formed by hoses or bellows; and        Ball-in-socket arrangements.        
The actuating mechanisms used by a firefighter to adjust these structural elements to a particular trajectory generally fall into these three classifications:                The structural elements are moved directly by human force, and remain stationary of their own accord or are secured with a means such as a locking knob, clamp, or friction slip clutch;        The structural elements are moved under mechanical advantage by a human-operated adjusting mechanism, such as a worm/worm wheel, lever, rack & pinion, screw, cables, chains, and push/pull rods; and        The structural elements are moved by force from an external source, such as a hydraulic, electric, pneumatic, or water powered drive motor with gear reduction, or by a cylinder, piston, or rotary actuator driven by oil from an external source or by water from within the monitor. These arrangements enable a firefighter to operate the monitor under power while either at the monitor or from a distance via wired or wireless operation.        
Fire monitors with a wide variety of configurations have been patented over the course of time. These configurations include combinations of a wide variety of different structural elements that provide adjustability of the trajectory, in combination with various mechanisms for firefighters to use to adjust the monitor to a particular trajectory or direction.
This invention relates generally to firefighting monitors that use pivotable conduit segments, and more particularly to firefighting monitors like those described in US reissue patent RE40441. The monitor illustrated in that patent has a plurality conduit segments in the form of ball-in-socket joints that provide at least one degree of freedom for swiveling the conduit segment under pressure. In that monitor, the forces due to water pressure and nozzle reaction are borne by the pair of orthogonally arranged pivoting conduit segments, and the forces of gravity are dealt with by means of a one-way brake. The monitor offers two degrees of freedom of movement, and permits a range of travel of +/−20 degrees in both the horizontal and vertical planes. The simplicity, compact size, ease of use, and relatively low manufacturing cost of the pivoting conduit segments has proven quite useful, and has been found to offer advantages over other means for adjusting trajectories in portable monitors.
Patent RE40441 taught that “additional ball and socket combinations could be added to the double ball and socket combinations to add additional range of motion in a pivoting connector”. Over time, it has become apparent that the additional range of motion suggested by the patent would prove useful. Patents such as U.S. Pat. No. 7,644,777 show efforts to increase the range of motion by using two or more consecutive pivoting conduit segments whose axes of rotation are substantially parallel. However, the nozzle reaction force acts upon the segments in such monitors in a way that causes the a downstream conduit segment to rotate with respect to an upstream conduit segment, creating, for example, a tendency for the discharge elevation to raise upwards by itself. Some have touted this tendency as a “safety feature” (because it stops unattended fire monitors from spraying at lower elevation angles), but others recognize that there are disadvantages in requiring the firefighter to exert a separate force to maintain the relative positioning of the downstream segment.
In these portable monitors, the downstream conduit segment places the nozzle reaction forces on a plane that passes above the horizontal axis between a midstream conduit segment and an upstream conduit segment, resulting in a net torque about that axis. This vertical offset also increases the overturning moment of the monitor, tending to make the front of the monitor lift off the ground and thus decreasing the stability of the monitor. Counterbalance devices described in the patents inhibit free range of travel for unattended operation of the monitor.
U.S. Pat. No. 7,802,630 shows an attempt to increase the range of motion of a firefighting monitor by using multiple pivoting fluid conduit segments in series. This monitor uses a series of identical ball-and-socket conduit segments that are each easy and cheap to manufacture. However, operation of the monitor at angles other than straight ahead results in an ever-increasing moment from nozzle reaction, which tends to straighten the assembly. With only a single actuator, the effects of nozzle reaction and gravity (which sometimes aggregate and sometime offset each other, depending upon the position of the conduit segments) tend to make the monitor whip from side to side as even slight misalignment from a straight position causes moments on the other conduit segments. On the other hand, using an actuator on multiple conduit segments (as described in connection with the embodiment seen in FIG. 6) makes the device expensive to manufacture and difficult to use.
Some of the disadvantages of these monitors were attempted to be addressed in US patent publication 2009-0277656, which shows a series of concentric pivoting elements that have a common axis of rotation. The illustrated monitor appears to be operable by hand, and would not move by itself under the forces of nozzle reaction. However, it is not evident that the pieces can be assembled as depicted, and the concept has serious flaws: the pieces are quite complex to machine from metal (even with a 5-axis CNC machining center) and each joint requires specialized seals to be molded (each of a different size). The elevation mechanism is far more complex than those used in swivel joint monitors from the same company, such as those depicted in U.S. Pat. No. 4,674,686.